As immunosuppressive agents, for example, cyclosporin, tacrolimus and the like that suppress the production of cytokines such as IL-2 are currently utilized. Furthermore, in recent years, compounds that suppress the activity of the immune system by inducing a decrease in the number of lymphocytes in the blood have been studied. For example, fingolimod does not show an action to suppress the production of cytokines in vitro, but is phosphorylated in the biological body and then acts as an S1P receptor agonist to thereby induce a decrease in the number of lymphocytes in the blood. By this way, the activity of the immune system is suppressed (for example, see Non-Patent Literature 1).
As a compound that induces a reduction in the number of lymphocytes in the blood by a mechanism other than that of S1P receptor agonists, 2-acetyl-4-tetrahydroxybutylimidazole (THI) is known (for example, see Patent Literature 1). THI induces a reduction in the number of lymphocytes in the blood by inhibiting S1P lyase (for example, see Non-Patent Literature 2, Non-Patent Literature 3 and the like).
As such S1P lyase inhibitors, besides THI, imidazole derivatives having a polyol as a substituent (for example, see Patent Literature 2, Patent Literature 3, Non-Patent Literature 4, Non-Patent Literature 5 and the like), imidazole derivatives to which a hetero ring is directly bound (for example, see Patent Literature 4, Patent Literature 5, Non-Patent Literature 4, Non-Patent Literature 5 and the like), and the like are known. Furthermore, as compounds that induce a reduction in the number of lymphocytes, thiazole derivatives having a polyol as a substituent (for example, see Patent Literature 6) and the like are known.